docs(examples): Show pacman-style help

Looking at how `App::usage` member is used, and didn't realize we had
this special logic.

examples/pacman.md

@@ -34,5 +34,54 @@ Searching for name...
 ```
 *(users can "stack" short subcommands with short flags or with other short flag subcommands)*
 
+In the help, this looks like:
+```console
+$ pacman -h
+pacman 5.2.1
+Pacman Development Team
+package manager utility
+
+USAGE:
+    pacman[EXE] <SUBCOMMAND>
+
+OPTIONS:
+    -h, --help       Print help information
+    -V, --version    Print version information
+
+SUBCOMMANDS:
+    -Q--queryquery    Query the package database.
+    -S--syncsync      Synchronize packages.
+    help              Print this message or the help of the given subcommand(s)
+
+$ pacman -S -h
+pacman[EXE]-sync 
+Synchronize packages.
+
+USAGE:
+    pacman[EXE] {sync, --sync, -S} [OPTIONS] [--] [package]...
+
+ARGS:
+    <package>...    packages
+
+OPTIONS:
+    -h, --help                  Print help information
+    -i, --info                  view package information
+    -s, --search <search>...    search remote repositories for matching strings
+
+```
+
+And errors:
+```console
+$ pacman -S -s foo -i bar
+? failed
+error: The argument '--search <search>...' cannot be used with '--info'
+
+USAGE:
+    pacman[EXE] {sync, --sync, -S} --search <search>... <package>...
+
+For more information try --help
+
+```
+
 **NOTE:** Keep in mind that subcommands, flags, and long flags are *case sensitive*: `-Q` and `-q` are different flags/subcommands. For example, you can have both `-Q` subcommand and `-q` flag, and they will be properly disambiguated.
 Let's make a quick program to illustrate.